The present invention relates to an AC plasma display apparatus (PDP apparatus) used in a display unit such as a personal computer or work station, a flat television, or a plasma display (PDP) for displaying advertisements, and information, etc.
One of commercially-available AC color PDPs is a three-electrode-type PDP in which a plurality of first electrodes and a plurality of second electrodes extending in a first direction are alternately provided in parallel and a plurality of third electrodes extending in a second direction perpendicular to the first direction are provided in parallel.
In a general structure of the three-electrode type PDP, first (X) electrodes and second (Y) electrodes are alternately provided in parallel on a first substrate, third (address) electrodes extending in the direction perpendicular to the first and second electrodes are provided on a second substrate facing the first substrate, and each surface of the electrodes is covered with a dielectric layer. Between the third electrodes on the second substrate, there are further provided one-directional stripe-shaped barrier ribs extending in parallel with the third electrodes or a two-dimensional grid-shaped barrier rib arranged in parallel with the third electrodes and the first and second electrodes so that the cells are separated from one another. After phosphor layers are formed between the barrier ribs, the first and second substrates are bonded together.
After the charges (wall charges) in the vicinity of the electrode in each cell are brought into a uniform state by applying a voltage between the first and second electrodes, a scan pulse is sequentially applied to the second electrode and an address pulse is applied to the third electrode in synchronization with the scan pulse and an addressing operation is performed to selectively leave the wall charges in the cell to be turned on. Then, by applying a sustain discharge pulse by which the two adjacent electrodes to be discharged become electrodes having alternately opposite polarities to perform the addressing operation, the cell to be turned on, in which the wall charges are left, makes a sustain discharge and is turned on. The phosphor layer emits light by the ultraviolet rays generated by the discharge, and the emitted light is seen through the first substrate. For this purpose, the first and second electrodes are each composed of an opaque bus electrode made of a metal material and a transparent electrode (discharge electrode) such as an ITO film, and the light generated in the phosphor layer is seen through the transparent electrode. Specifically, a plurality of first bus electrodes and a plurality of second bus electrodes extending parallel in a first direction are alternately disposed, and transparent first and second discharge electrodes are provided between the first and second bus electrodes facing each other. The first discharge electrode is electrically connected to the first bus electrode, whilst the second discharge electrode is electrically connected to the second bus electrode. The first and second discharge electrodes may be solid electrodes parallel to the first and second bus electrodes or may have shapes protruding from the first and second bus electrodes. In the first and second discharge electrodes protruding from the first and second bus electrodes for each display cell, edges of these electrodes facing each other are parallel to the first direction and form a parallel slit with constant width (slit width), whereby the discharge occurs across the slit. This slit is hereinafter also referred to as a “discharge slit”.
Although the parallel discharge slit having a straight-line shape as described above is generally used, it is proposed that the discharge slits are formed into various shapes. For example, Japanese Patent Laid-Open Publication No. 2004-71219 (“Patent Document 1”) discloses a shape in which the slit width is gradually varied in each cell. Thereby, high luminance can be obtained without increasing discharge voltage, and uniform discharge can be obtained at every cell.
In a color PDP, phosphor layers with three colors, R, G, and B are provided on three display cells adjacent to one another in the first direction so as to be distinguished respectively. By these three RGB display cells, one color pixel is formed. In view of display quality, it is desirable that color pixels be arranged with approximately the same pitch on a display screen. In each RGB display cell, width (length) of the first direction in which the first and second bus electrodes extend and width (length) of a second direction perpendicular to the first direction become approximately 1:3 ratio. That is, the display cell has an elongated shape extending in the second direction (vertical direction). Therefore, as described above, in the structure where the first and second discharge electrodes extend from the first and second bus electrodes and a discharge slit whose edges opposite to the first and second discharge electrodes are parallel to the first direction is formed, the length of the discharge slit (the length of the facing edges) is short. Therefore, there is the problem in which a discharge region is narrow and sufficient luminance cannot be obtained. Also, there is another problem in which the length of the discharge slit is shorter as the cell is smaller, whereby the discharge voltage is increased.
Japanese Patent Laid-Open Publication No. 7-320644 (“Patent Document 2”), No. 11-86739 (“Patent Document 3”), and No. 2001-110324 (“Patent Document 4”) disclose an electrode shape in which: the first and second discharge electrodes alternately extend like teeth of a comb from the first and second bus electrodes, respectively, and are opposite to the edges extending in the second direction perpendicular to the first direction in which the first and second bus electrodes extend; and the discharge slit extending in the second direction (vertical direction) is formed. FIG. 1 is a view showing a conventional example of the electrode shape in which the vertical discharge slit disclosed in the Patent Document 2 is formed. As shown in FIG. 1, first (sustain) electrodes 102 and second (scan) electrodes 101 are formed like the teeth of a comb. Third (address) electrodes 103 are provided so as to overlap with portions of the second electrodes 101 extending in the second direction. The address discharges occur in portions shown by reference symbol “W”. For the charges to be accumulated by the address discharges, the sustain (display) discharges are spread in regions shown by reference symbol “S”. Note that the Patent Document 2 does not describe, for example, that the bus electrodes are formed by metal layers and transparent electrodes are formed by ITO films. Also, in the Patent Document 2, the first and second electrodes 102 and 101 are close to each other even in the slit that does not discharge, so that there are the problem in which power required in applying the voltage to the panel is increased.
According to the above-mentioned electrode shape (the shape of the vertical discharge slit extending in the second direction), the first and second discharge electrodes face each other over an entire region of the vertically-extending display cell and at the short distance via the discharge slit. Therefore, the voltage for sustaining the discharge can be reduced, so that the discharging region becomes wide and the high luminance is obtained.
To form the vertically-extending discharge slit in the second direction described above, the first discharge electrode and the second discharge electrode have to be extended so as to be spaced a predetermined distance apart from each other in the vertically-extending display cell. Therefore, the shapes of the first and second discharge electrodes become extremely elongated, whereby there is the problem such that disconnection occurs easily. To solve this problem, the above-mentioned Patent Document 2 discloses a structure in which the first and second discharge electrodes are integrally formed with those of the adjacent respective display cells, namely, the discharge electrodes are shared between the adjacent display cells. This structure makes it possible to widen the electrode width and reduce the occurrence of the disconnection.
Also, as described above, the commercially-available conventional AC color PDP mainly has a structure in which two electrodes (X, Y) causing repetitive discharges (sustain discharges) are each constituted by a transparent electrode (discharge electrode) and a metal electrode with a low resistance value (bus electrode) and a gap between these two electrodes (X, Y) for discharge (discharge slit) is approximately parallel to a direction in which the metal electrode extends (first direction). Meanwhile, in the PDP, a square pixel is divided into three portions in the direction in which the metal electrode extends (first direction), and these portions are assigned to cells of three colors, R, G, and B, respectively. Therefore, in one cell, the length (the first-directional distance) of the facing edges of the two electrodes (X, Y) becomes short. Note that the square pixel is a pixel, which is composed of three cells of R, G, and B and has an approximately square shape when viewed from a direction perpendicular to the PDP surface. As the PDP is more finely fabricated, the above tendency becomes more apparent. For this reason, there is proposed the structure (the above-mentioned vertically-extending discharge slit) in which the transparent electrode is drawn to a direction (second direction) perpendicular to the direction in which the metal electrode extends (first direction) and the slit between the two electrodes (X, Y) is provided so as to extend in a direction (second direction) approximately perpendicular to the metal electrode. Such a technique is described in Japanese Patent No. 3144987 (“Patent Document 6”).